I'm uncertain what your sentence here means:

The files is always in this formate where the line i want is right after the line couldn't parse

but as to a general method to use, consider this:

use strict;

open(FILE,"myfile") or die "couldn't open input file";

open(OUTFILE,">myotherfile") or die "couldn't open output file";

my @file_lines = <FILE>;

for( @file_lines )
{
  print OUTFILE $_ if /matches_this_pattern/;
}
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